Pneumatic motion-checking device and door operating system including same



Nov. 28, 1961 E. P. CODLING PNEUMATIC MOTION-CHECKING DEVICE AND DOOR fl 2a a0 54- as 56 pi P atent fitice 3,019,433 Patented Nov. 28, 1961 PNEUMATIC MOTION -CHECKING DEVICE AND DOOR OPERATING SYSTEM INCLUDING SAME Eldred P. Codling, Norwood, Mass, assignor to National Pneumatic Co., Inc., Boston, Mass, a corporation of Delaware Filed Mar. 18, 1958, Ser. No. 722,184 9 Claims. (Cl. 121--38) The present invention relates to a pneumatic pistoncylinder assembly in which the piston is comparatively free to move in one direction and in which the movement of the piston in the other direction is controllably checked over substantially its entire range of travel, and to a door checking or operating system including the said assembly.

It is conventional, in cylinder and piston assemblies, with and without power actuation, to provide for checking the movement of the piston in a given direction. in the case of power operated doors it is often desired that the movement of the door in one direction be slower than its movement in the other direction. For example, it is often desired that a power-operated door open quickly and close slowly. In other instances doors are opened manually and a power source such as a stretched spring is relied upon to cause the door to close when manual pressure is released therefrom, If no check means is provided the door many tend to close so rapidly as to be hazardous, and it may tend to slam to closed position with such force as to be self-destructive or to constitute a nuisance.

These problems are particularly acute in connection with the control of doors on public conveyances such as buses, trolleys and trains. Whether these doors are power moved to open position under the control of the operator of the vehicle or, as is presently becoming preferred, they are manually pushed to open position by patrons wishing to alight from the vehicle, some power means, most conveniently a spring, is employed to urge the door to return to closed position. When a passenger alighting from a vehicle releases a door which he has pushed open, and if that door moves toward closed position too rapidly, particularly during the initial portion of its travel, it may strike a second passenger who is alighting and cause him injury.

The conventional way in which checking is achieved is by providing, in the end of the cylinder toward which the piston moves when checking is desired, a mechanism which will restrict the flow of fluid out from the cylinder but will permit fluid to enter the cylinder which will restrict the flow of fluid to enter the cylinder more readily. When a substantially incompressible fluid is caused to move in and out of the cylinder the checking or throttling action will be substantially uniform throughout the travel of the piston. However, hydraulic systems using incompressible fluid are expensive, the almost inescapable likelihood of fluid leakage makes for maintenance problems and often rules out the use of such systems in locations Where leakage cannot be tolerated, and the comparative sensitivity of the incompressible fluid to temperature conditions causes the system to operate differently at diflerent times and in diiterent places. Accordingly pneumatic systems, utilizing a compressible fluid, usually air, are much preferred for this purpose.

Hower, When a compressible fluid is employed in the cylinder the checking or throttling function above described is by no means as satisfactory or effective as when an incompressible fluid is employed. Consider the case of a simple door check, a device designed to permit the door to be moved freely in one direction (opening) and to move more slowly in the other direction (closing) when urged in that other direction by some external force (a tension spring). When the door opens the piston moves in a first direction within the cylinder. The cylinder is so designed that as the space within the cylinder on the trailing side expands, air freely enters that space so as not to retard the movement of the piston. When the piston moves in the opposite direction that space, now large in volume and full of air, is contracted and means are provided to restrict the escape of air from that space. However, there will be substantially no retardation of the initial major portion of the travel of the piston (and hence of the door) because, due to the initial large Volume of the space, the piston must travel an appreciable distance before any effective back pressure is built up inside the cylinder. And this portion of the travel of the piston when used as a door check is, it will be remembered, during the time that the door restoring force (spring) at its maximum. Accordingly, the door will tend to move rapidly toward closing position over an appreciable arc. The back pressure within the cylinder will be increasing and the restoring force will be decreasing, and at some point the door will suddenly slow down and then move slowly toward its closed position. Moreover, if the door is not completely opened this delay in the development of a satisfactory back pressure may Well result in a complete absence of checking action, the door slamming closed.

The initial rapid movement of the door, of course, constitutes a source of hazard. Nevertheless none but the most complicated means have been known in the past for minimizing this initial rapid movement of the door in connection with a pneumatic system. It will not suflice to further restrict the ease withwhich air can escape from the cylinder. Even if air were not permitted to escape at all the door would still move initially in a rapid manner for an appreciable distance. Moreover, the more restricted the air escape passage is made the more difficult it is for the door to reach its fully closed position.

I have discovered that by a mechanically simple modification of existing power or checking pneumatic cylinders involving the use of a compressible fluid, these undesirable attributes of prior art pneumatic systems can be completely eliminated. The movement of the door will be checked throughout its entire range of travel, and in a readily controllable manner. The checking action will be effective even if the door is opened only part way and then permitted to close. The door closing speed can be made to be substantially uniform and within desired limits, as is generally preferred, or, if desired, the last portion of its movement can even be made exceptionally slow without detracting from the desired speed of the initial portion of the door movement. The device of my invention is particularly well adapted for use as a simple and inexpensive door check, but it can very readily be used without modification as part of a system in which the door is pneumatically driven to open position.

If a pair of flow control or fluid admitting means are employed, one at each end of the cylinder, with their flow control characteristics properly coordinated, a checking effect can be obtained in a pneumatic system which is superior to that obtainable in a simple hydraulic system using incompressible fluid, and which permits the attainment of the advantages above set forth. More specifically, the flow control means at that end of the cylinder away from which the piston moves when its movement is to be relatively unrestricted is so constructed as to permit comparatively unrestricted flow of compressible fluid into the cylinder and to provide for comparatively restricted or throttled flow of the fluid out from the cylinder. The flow control means at the other end of the cylinder, the end toward which the piston moves when the piston is to move freeely, is so constructed as to permit comparatively free escape of fluid from the cylinder but to provide for comparatively restricted or throttled flow of fluid into the cylinder.

This is by no means the same as producing a more intensive throttling effect with the type of single control valve used in the prior art. Such an expedient will not have any appreciable effect on the initial movement of the doors and will cause a final movement of the doors to be too slow. With the present system, however, during the time that the second mentioned valve, toward which the piston is moving, is inefiective (the initial portion of the piston travel in the direction in which movement is to be checked) the first valve is effective to reduce the closing speed to an acceptable value. By appropriate setting the second mentioned valve can be made to control the latter portion of the door in order to further reduce the speed of door movement, or a substantially uniform door speed can be obtained substantially throughout its range of travel. Moreover, the door speed will be independent of the initial position of the door, e.g. whether is has been fully or only partially opened.

When this device is incorporated into a power system for controlling the movement of doors the door movement in the direction to be checked will be substantially uniform and will be adequately retarded, and this without presenting any difficulties insofar as reliability of movement of the door to a fully closed position is concerned.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to a cylinder-piston assembly in which movement of the piston is comparatively free in one direction and is checked in the other direction, and to a door operating system in which such a device is included, all as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in which:

FIG. 1 is a top plan view of an operating system for a push-actuated door which is spring urged to return to closed position, in which the present invention is embodied;

FIG. 2 is a top plan view, on an enlarged scale, and partially broken away, showing the piston-cylinder as sembly used in such a system for permitting free movement of the doors to open position and for checking or retarding their return movement to closed position;

FIGS. 3 and 4 are cross sectional views taken along the lines 3-3 and 44 respectively of FIG. 2 and showing the internal construction of the flow control valves at the opposite ends of the cylinder; and

FIG. 5 is a schematic diagram illustrating the manner in which the cylinder of FIG. 2 can be used in a system which is designed to open the door through the use of pneumatic power. V

The present invention, insofar as the checking piston and cylinder assembly is concerned, is here illustrated as embodied in a push door actuating mechanism suitable for use in a public transportation vehicle, but it Will be understood that the applicability of the instant invention in its broader aspects is not limited thereto.

Some of the details of the mechanism here illustrated are disclosed and claimed in copending application Ser. No. 720,772, filed March 11, 1958, by Kristupas Daugirdas, entitled Door Controlling Linkage, and assigned to the assignee of this application, now Patent No. 2,893,- 506, issued on July 7, 1959.

Having reference first to the push door operating system as a whole, which is illustrated in FIG. 1, the doors 2 (shown only in phantom and in the position which they will assume when they are pushed open) are mounted beneath base plate 4 so as to pivot about axes 6 between the open position shown in phantom and a closed position extending toward one another substantially at right angles to their open positions. They are connected at their upper ends to arms 8 mounted above the base plate 4 (shown in solid lines in their door-closed position and in phantom in their door-open position), these arms being pivotally connected at 10 to links 12 which are in turn pivotally connected, at 14, to arms 16 fast on shaft 18. Also fast on shaft 18 is arm 20 pivotally connected at 22 to link 24 to which is connected the piston rod 26 which extends into cylinder 28 by passing sealingly through the cylinder end cap 30, a piston 32 being connected to the rod 26 inside the cylinder 28 and being slidable back and forth Within the cylinder in sealing relation thereto. The other end of the cylinder 28 is closed by end cap 34 which is pivotally mounted on the base plate 4 at 36. The end caps 30 and 34 are provided with individual fluid admitting or flow control means generally designated 33 and respectively, the details of which will be described below. The arm 20 is also connected, at 42, to one end of a tension spring 44 the other end of which is adjustably anchored to the base plate 4 at 46.

The linkage is shown in FIG. 1 in its position corresponding to the doors 2 being closed. When the doors 2 are pushed open the right and left hand doors will pivot in clockwise and counter-clockwise directions respectively to their open positions shown in phantom, the arms 8 will correspondingly pivot to their positions shown in phantom, and the arm 20 will be rotated in a counterclockwise direction, causing the piston 32 to move from the right to the left (from end cap 30 toward end cap 34), while the spring 44 will be stretched. When the doors are released the spring 44 will take over and contract, returning the linkage to its illustrated position and causing the piston 32 to move toward the right (from end cap 34 toward end cap 30).

The precise form and construction of the fluid admitting or flow control means 38 and 40 may take any desired form, and many arrangements are known to permit the accomplishment by the means 38 and 40 of their desired function, to wit, to permit comparatively free flow of a compressible fluid such as air in a given direction relative to the cylinder 28 and to provide for restricted or throttled flow of the fluid in the opposite direction. More specifically, the admitting means 38 should, in the embodiment here illustrated, provide for free flow of air into the cylinder 28, as indicated by the solid arrow 48 in FIG. 2, and throttled or restricted flow of air out from the cylinder 28, as indicated by the broken arrow 50. The admitting means 40 should provide for free flow of air out from the cylinder 28, as indicated by the arrow 52, and for throttled or restricted flow of air thereinto, as indicated by the arrow 54.

The means 38 and 40 are here sepecific-ally illustrated in the form of a conventional flow control valve available as such on the open market. These valves comprise a casing 56 having a central bore 58 provided with screw threads 60 and 62 at its ends for connection to appropriate pipes. The two ends of the bore 58 are separated by an internal partition 64 provided with two apertures 66 and 68. A ball valve 70 is provided on one side of the partition 64 opposite the aperture 66 and is spring urged into sealing relation with that aperture by means of spring 72 the tension of which may be adjusted through rotation of screw 74. A tapered plug 76 is positioned on the other side of the partition 64 and opposite the aperture 68 and adjustably protrudes into that aperture through rotation of its outwardly extending and 78, the plug 76 being threadedly engaged with the valve casing. As a result flow of air from the end 60 toward the end 62 will lift the ball valve 70 from its seat in the aperture 66 and thus provide for relatively free passage of air, whereas air moving'in the opposite direction from end 62 to end 60 will urge the ball valve 70 onto its seat and thus can pass only through the restricted clearance between the plug 76 and the aperture 68. A comparison of FIGS. 3 and 4 will reveal that the valves defining the air admitting means 38 and 40 are structurally identical and are merely reversed in positon, the valve defining the air admitting means 38 having its end 62 connected to fitting 80 which communicates with the interior of the cylinder 28 on the right hand side of thepiston 32, while the valve constituting the air admitting means 40 has its end 60 connected to fitting 82 which communicates with the interior of the cylinder 28 at the left hand side of the piston 32.

Consequently, when the piston 32 is moved to the left, as it will be when the doors 2 are opened, its movement will be relatively unimpeded, since the air pushed by the piston 32 can freely escape through the means 40 and air sucked into the cylinders 28 by the piston 32 can freely enter through the means 38.

When the piston 32 commences to move to the right, as it will under the influence of the spring 44 when manual pressure is released from the doors 2, it will tend to compress the substantially large volume of air between itself and the end cap 30, since the escape of that air is restricted by the means 38. During over approximately the first half of the movement of the piston 32 no appreciable retardation of piston movement will result therefrom because of the appreciable magnitude of the volume of air involved. However, as soon as the piston 32 moves away from the end cap 34, which it closely approached when the doors were opened, a substantial suction will almost immediately be produced on the left hand side of the piston 32 because of the restriction on the entry of air into the cylinder 28 through the means 40. Thus the initial movement of the piston 32 to the right (and hence the initial movement of the doors toward closed positon) will be checked. As the volume of .the space to the left of the piston 32 increases the relative magnitude of the checking effect produced by the means 40 will decrease (for a given movement of the piston), but at the same time the volume of the space to the right of the piston 32 is decreasing and hence the checking effect of the means 38 is increasing (for a corresponding movement of the piston). The closing force exerted by the spring 44 is decreasing as the doors approach closed position. The magnitudes of these checking elfects with relation to the force urging the doors closed can be con.- trolled through adjustment of the plugs 76 of means 38 and 40 respectively. Thus it is possible to obtain checked movement of the doors 2 to closed position at a substana tially constant speed throughout their entire range of travel. The speed of movement con be adjusted to any desired value and it is even possible, through appropriate settings of the means 38 and 40, to provide for a given speed of movement of the door during its initial period of return to closed position and a diiferent rate of move.- ment of the door during the latter part of its travel toward closed position. I am thus able to obtain a checking action in a pneumatic system which is at least as good as, and in many respects better than, the checking obtainable in an hydraulic system, but at considerably less expense and without any of the disadvantages usually associated with hydraulic systems.

As thus far described the piston-cylinder assembly 28, 32, 38, 40 has been used in connection with doors which are manually opened and power closed. That very assembly, without any modification whatsoever, may readily be used in a system in which pneumatic power is provided for opening the door, as is schematically illustrated in FIG. 5. All that is necessary is to connect the end 60 of the air admitting means 38, as by conduit 84, to a valve 86 which is capable of selectively connecting the conduit 84 either to pipe 88 connected to -a suitable source of pneumatic fluid under pressure or to pipe 90 connected to exhaust. The valve 86 may be actuated in any desired manner, as by means of solenoid 92. When the conduit 84 is connected to pipe 88 air under pressure will pass through the admitting means 38 and force the piston 32 to the left, this cor-responding to the manually pushed operation in the previously described embodiment. When the valve 86 is actuated to connect the conduit 84 to the pipe 90, and therefore to exhaust, the device func- 6 tion in precisely the same manner as has been previously de cribe It will therefore be seen that the device and system of the present invention are simple in the extreme yet achieve operational results the obvious desirability of whichhas long been recognized but which the prior art has not been able to obtain in a pneumatic system, and which it could obtain in an hydraulic system only at the cost of appreciable trouble and expense.

While but a limited number of embodiments of the present invention have been here disclosed, it will be understood that many variations may be made therein, all within the spirit of the invention as defined in the following laims.

I claim:

1. In the combination of a door movable between closed and open positions, a cylinder, a piston slidable therein, means directly connecting said piston and door for substantially simultaneous movement, said piston sliding in one direction when the door is opened and in the other direction when the door is closed, and a source of compressible fluid, the improvement which comprises first fluid passage means canied by said cylinder at one operative end thereof for conducting said compressible fluid from said source to said cylinder on the side of said piston toward which said piston moves when said door closes, said first means permitting comparatively free flow into said cylinder and comparatively restricted flow out therefromfand second fluid passage means carried by said cylinder at the other operative end thereof for conducting said compressible fluid from said source to said cylinder on the side of said piston toward which said piston moves when said door opens, said second means permitting comparatively free flow out from said cylinder and comparatively restricted flow thereinto, whereby said combination permits comparatively free opening movement of said door and checks the closing movement thereof throughout substantially its entire range of travel.

2. The combination of claim 1, in which said source is the atmosphere, both of said fluid passage means connecting the respective sides of said piston thereto.

3. The combination of claim 1, in which said compressible fluid reaches both of said fluid passage means at substantially the same pressure.

4. The combination of claim 1, in which said source is in two parts, the first containing a compressible fluid under comparatively high pressure and the second containing a compressible fluid under comparatively low pressure, said first source part being connected to said firstfluid passage means via a controllable valve capable of s l c i e y conn g a t id Pa ag mea to said first source part or to exhaust, said second source part being connected to said second fluid passage means.

5. In the combination of a cylinder, a piston slidable therein, means for moving the piston, a source of compressible fluid, and fluid passage means for conducting said compressible fluid from said source to said cylinder on both sides of said piston; the improvement which comprises that portion of said fluid passage means active on one side of said piston permitting comparatively free flow into said cylinder and comparatively restricted fiow out therefrom, that portion of said fluid passage means active on the other side of said piston permitting comparatively free flow out from said cylinder and comparatively restricted flow thereinto, whereby said piston may move freely in the direction of said other side thereof and the movement of said piston in the direction of said one side thereof is checked throughout substantially its entire range of travel, said source being in two parts, the first containing a compressible fluid under comparatively high pressure and the second containing a compressible fluid under comparatively low pressure, said first source part being connected to said fluid passage means portion for said one side of said piston via a controllable valve capable of selectively connecting said fluid passage means portion to said first source part or to exhaust, said second source part being connected to said fluid passage means portion for said other side of said piston.

6. In combination, a door movable between closed and open positions, a cylinder, a piston slidable therein, means connecting said piston and door for substantially simultaneous movement, said piston sliding in one direction when the door is opened and in the other direction when the door is closed, a source of compressible fluid, first fluid passage means for conducting said compressible fluid from said source to said cylinder on the side of said piston toward which said piston moves when said door closes, said. first means permitting comparatively free flow into said cylinder and comparatively restricted flow out therefrom, and second fluid passage means for conducting said compressible fluid from said source to said cylinder on the side of said piston toward which said piston moves when said door opens, said second means permitting comparatively free flow out from said cylinder and comparatively restricted flow thereinto, whereby said combination permits comparatively free opening movement of said door and checks the closing movement thereof throughout substantially its entire range of travel, said source being in two parts, the first containing a compressible fluid under comparatively high pressure and the second containing a compressible fluid under comparatively low pressure, said first source part being connected to Said first fluid passage means via a controllable valve capable of selectively connecting said first fluid passage means to said first source part or to exhaust, said second source part being connected to said second fluid passage means.

7. In the combination of a cylinder, a piston slidable therein, means for moving the piston, a source of compressible fluid, and fluid passage means carried by said cylinder at opposite operative ends thereof for conducting said compressible fluid from said source to said cylinder on both sides of said piston; the improvement which comprises that portion of said fluid passage means active on one side of said piston permitting comparatively free flow into said cylinder and comparatively restricted flow out therefrom, that portion of said fluid passage means active on the other side of said piston permitting com paratively free flow out from said cylinder and comparatively restricted flow thereinto, whereby said piston may move freely in the direction of said other side thereof and the movement of said piston in the direction of said one side thereof is checked throughout substantially its entire range of travel, in which said source is in two parts, the first containing a compressible fluid under comparatively high pressure and the second containing a coma pressible fluid under comparatively low pressure, said first source part being connected to said fluid passage means portion for said one side of said piston via a controllable valve capable of selectively connecting said fluid passage means portion to said first source part or to 8 exhaust, said second source part being connected to said fluid passage means portion for said other side of said piston. I

- 8. In the combination of a cylinder, a piston slidable therein, means for moving the piston, a source of compressible fluid, and fluid passage means for conducting I said compressible fluid from said source to said cylinder on both sides of said piston; the improvement which comprises that portion of said fluid passage means active on one side of said piston permitting comparatively free flow into said cylinder and comparatively restricted flow out therefrom, that portion ofsaid fluid passage means active on the other side of said piston permitting comparatively free flow out from said cylinder and comparatively restricted flow thereinto, whereby said piston may move freely in the direction of said other side thereof and the movement of said piston in the direction of said one side thereof is checked throughout substantially its entire range of travel, said source being in two parts, the first containing a compressible fluid under comparatively high pressure and the second containing a compressible fluid under comparatively low pressure, said first source part being connected to said fluid passage means portion for. said one side of said piston, said second source part being connected to said fluid passage means portion for said other side of'said piston, one of said source parts being connected to its corresponding fluid passage means portion via a controllable valve capable of selectively connecting said fluid passage. means portion to said source part or to exhaust.

9.- In the combination of a cylinder, a piston slidable therein, means for moving the piston, a source of compressible fluid, and fluid passage means for conducting said compressible fluid from said'source to said cylinder on both sides of said piston; the improvement which comprises that portion of said fluid passage means active on one side of said piston permitting comparatively free flow into said cylinder and comparatively restricted flow out therefrom, that portion of said fluid passage means active on the other side of said piston permitting comparatively free flow out from said cylinder and comparatively restricted flow thereinto, whereby said piston may move freely in the direction of said other side thereof and the movement of said piston in the direction of said one side thereof is checked throughout substantially its entire range of travel, said source being connected to one of said fluid passage means portions via a controllable valve capable of selectively connecting said fluid passage means portion to said source or to exhaust.

References Cited in the file of this patent UNITED STATES PATENTS Re. 14,674 Schmidt June 24, 1919 1,036,340 Rockwell Aug. 20, 1912 1,714,545 Burns May 28, 1929 2,262,432 Rodder et al. Nov. 11, 1941 2,835,488 Hubbell May 20, 1958 

